The proper height of the bicycle seat for the cyclist is when one of the legs of the cyclist is straight while the pedal is located at the lowest position. The correct height of the bicycle seat is important to let the cyclist operate the bicycle comfortably.
It requires a significant cost to have a custom-made bicycle frame because of the different sizes of the cyclists so that the bicycle seat adjustable device is needed to adjust the height of the seat according individual needs of the cyclist.
The conventional seat adjustable devices generally include mechanical adjustable devices, hydraulic adjustable devices, and hybrid adjustable devices which use air and hydraulic liquid. The mechanical adjustable devices use mechanical parts to set the relative height between the seat and the seat tube. The hydraulic adjustable devices use hydraulic liquid such as oil or air cooperated with paths to achieve the purpose of adjustment of the seat. The hybrid adjustable devices utilize both air and hydraulic liquid to adjust the height of the seat relative to the seat tube.
The air is compressible and the hydraulic oil movable in the paths in the adjustable device so as to allow the seat post and seat tube to have relative and linear movement to position the proper height of the seat.
One of the hydraulic seat adjustable devices is disclosed in Taiwan Utility Patent Application No. 089221346 and comprises a locking part to which a lever and a guide rod are respectively connected. The guide rod includes a passage and a movable rod is movably located in the passage. The movable rod has one end extending out from the central hole in the locking part and contacting against an end of the lever. A spring is mounted to the movable rod and located between the lever and the locking part. A hollow tube is mounted to the guide rod and a pressure tube is located in the hollow tube. A piston is located in the pressure tube, a front action rod and a rear action rod are located in the piston. The front and rear action rods are cooperated with the pressure rings and control holes to control the movement of the guide rod. A head frame is mounted to the hollow tube and the threaded rod is threadedly connected to the two side threaded holes in the head frame. Two adjustable blocks are forcibly inserted into the hollow tube and an engaging block is engaged with the hole of the hollow tube.
Because the pressure tube is located in the hollow tube, and the front and rear action rods in the pressure rod are cooperated with multiple pressure rings to urge the guide rod or to move the guide rod, the user can adjust the seat directly by pulling the lever. However, the device lacks detailed description of the positions where the air or oil fills, the patterns of action of the oil or air are not disclosed.
Another one of the hydraulic seat adjustable devices is disclosed in Taiwan Utility Patent Application No. 097206782 and comprises a seat tube in which a seat post is linearly and movably inserted. A seat is connected to the top of the seat post. An adjustable device is located in the seat post and includes a base tube which is fixed to the seat tube and includes a top opening. An adjustable tube is located in the base tube. An adjustable frame is located beneath the adjustable tube and is co-movable with the adjustable tube. The adjustable tube defines an upper space and a bottom space in the base tube. A path is defined between the adjustable tube and the adjustable frame so as to communicate the upper and bottom spaces. A valve rod movably extends through the adjustable tube so as to open or close the passage, by this arrangement, the seat tube and the base tube have relative movement to adjust the position of the seat.
However, the hydraulic oil has to move between the two spaces to keep the pressure balance in the spaces, when the hydraulic oil flows fast within a short time between two different pressures, the pressure in one of the spaces may become too low to delay the movement of the adjustment of the seat.
The present invention intends to provide a bicycle seat adjustable device which does not change the sizes of the seat tube and seat post, and the hydraulic oil and air can be utilized to smoothly adjust the height of the seat.